Switchgear configurations have current limits based on the heat rise over ambient room temperature. It is generally desired to limit the maximum temperature of the hottest spot on the switchgear main bus to 105° C. (a rise of 65° C. over an assumed ambient temperature of 40° C.), as directed by the standard IEEE 37.20.2. Typical medium and high-voltage metal-clad switchgear arrangements have maximum continuous current ratings of about 3000 A, due to heat generation. It is desirable to increase this current rating to about 4000 A.
Since these switchgears must be arcing fault resistant, it is exceedingly difficult to dissipate heat losses caused by the nominal currents inside the switchgear compartments. Currently heat losses are dissipated either by radiation and convection from the current path to the enclosure and then to the ambient environment. Such heat transfer processes are inefficient and, as a result, the switchgear product is usually thermally limited by its nominal current.
Thus, there is a need to provide a cooling apparatus for a switchgear that cools the primary contacts and also reduces the temperature increase along current paths including busbar joints.